CacheStorage.has

The has() method of the CacheStorage interface returns a Promise that resolves to true if a Cache object matches the cacheName.

Syntax

caches.has(cacheName).then(function(true) {
  // your cache exists!
});

Returns

a Promise that resolves to true if the cache exists or false if not.

Parameters

cacheName

A DOMString representing the name of the Cache object you are looking for in the CacheStorage.

Examples

The following example first checks whether a cache called 'v1' exists. If so, we add a list of assets to it. If not (meaning the has() promise would reject) then we run some kind of cache set-up function.

caches.has('v1').then(function(hasCache) {
  if (!hasCache) {
    someCacheSetupfunction();
  } else {
    caches.open('v1').then(function(cache) {
      return cache.addAll(myAssets);
    });
  }
}).catch(function() {
  // Handle exception here.
});;

Specifications

Specification	Status	Comment
Service Workers The definition of 'CacheStorage' in that specification.	Working Draft	Initial definition.

Browser compatibility

[1] Service workers (and Push) have been disabled in the Firefox 45 Extended Support Release (ESR.)

See also

• Using Service Workers
• Cache
• WorkerGlobalScope.caches